1. Field of the Invention
This invention relates to a polyolefin composite material containing a polyolefin-based resin and a layered clay mineral, a method for producing the polyolefin composite material, and a formed product obtained by melt forming the polyolefin composite material.
2. Related Background Art
With the aim of improving the mechanical properties of polyolefin-based resins such as polypropylene, attempts have been made to incorporate a layered clay mineral, as a filler, into these resins. Japanese Patent Application Laid-Open No. 1998-182892 (Document 1) discloses a clay composite material comprising a polyolefin-based oligomer containing a functional group, an organic layered clay mineral hydrogen-bonded to the functional group, and a polyolefin resin, intended for dispersing a layered clay mineral satisfactorily in polyolefin, the layered clay mineral and polyolefin having poor compatibility with each other. The clay composite material described in Document 1 uses the polyolefin-based oligomer containing a functional group, such as a maleic anhydride group, a hydroxyl group, a carboxyl group, an amido group, an amino group, a urethane group, an ester group, an imido group, a maleimido group, a halogen group, an ether group, a thiol group, or an epoxy group. However, this clay composite material has been minimal in the effect of improving heat distortion temperature, and has been still insufficient in terms of impact resistance.
Z. W. Wang et al., “Exfoliated PP/Clay Nanocompsites Using Ammonium-Terminated PP as the Organic Modification for Montmorillonite”, Macromolecules, Vol. 36, No. 24 (2003), pp. 8919-8922 (Document 2) discloses polypropylene/clay nanocomposite materials using polypropylene having an ammonium group at the terminal. The polypropylene/clay nanocomposite materials described in Document 2 use ammonium-terminated polypropylene having a number average molecular weight of 58,900. However, these nanocomposite materials have been minimal in the effect of improving rigidity and heat distortion temperature, and have been still unsatisfactory in that impact resistance is low.